What kind of skimmer do you have? You'd have to have some really pristine water not to get skimmate. Sounds like a skimmer problem (I'm suffering with this right now too).
As for not going RO
... I'm sorry, but that's the only way you're going to eliminate the "WT? is in my water" issue. The good news is that at least that water is supposed to be drinkable so the worst you should end up with using that would be a cyano
/hair algae outbreak.
With your next fish... Before you transfer the fish into your system, please make sure that your pH and SG
match. If they don't match dump 1/2 of the water out and let it keep dripping (or keep moving shot glass at a time, one every 5 minutes depending on your method) until you get the parms matched.
I'd start over with the water but you should have enough bacteria established not to have to go through the cycle again.
Good luck. I hope this solves your problem once and for all. At least you're not using 40$ fish!